10
THE ESSEX NATURALIST
antiquus is believed to have lived in a wooded or forest environ-
ment and M. primigenius in a more open alluvial plain area
with fen vegetation at the Aveley site. Alternatively, the foot
of sediment separating them may include a non-sequence invol-
ving a considerable period of time in which the climate deteri-
orated.
Secondly, some controversy exists concerning the details of
the Last Interglacial sequence of terrace deposits in the Thames
tidal reaches, and the Aveley site offered important new evi-
dence in this connection. Estuarine terraces are. almost hori-
zontal and correspond to average high water mark in the tidal
reaches, whereas non-tidal terraces curve and follow the river
profile (Zeuner, 1959). Topographical evidence suggests that
there are two distinct terraces of Last Interglacial age in the
Thames tidal reaches, the terrace at Ilford (West, Lambert &
Sparks, 1964) with deposits lying up to 40-50 ft (12.2-15.2 m) OD,
and the so-called Upper Flood Plain Terrace with deposits up to
about 30 ft (9.1 m) OD at Brentford (Zeuner, 1959) and Trafalgar
Square (Franks, 1960). The mammalian faunas of these two
apparently different terraces seem distinct (Sutcliffe, 1964) but
there is no palaeobotanical evidence for such a separation. This
has led botanical workers to regard the Ilford and Trafalgar
Square sites as parts of the same terrace.
During the excavation of the elephants, a section across the
cut was drawn by Mr G. R. Ward, at about TQ 552807. The
deposits in the measured section rested on a bench of London
Clay at 5 ft (1.5 m) OD, going up to 49 ft (15 m) OD at the
highest point. The general sequence revealed in the cut is
given below and the position of the mollusc-bearing samples is
indicated.
ft. in. (m)
Yellow sand, removed by pit excavation process .......... 12 0